The present invention relates to a coating film forming method and to a coating apparatus for forming a coating film such as a photoresist film or an anti-reflective coating film by applying a coating solution to a substrate such as a glass substrate for a liquid crystal display (LCD) device.
In the manufacturing process of an LCD device, a photolithography technology is employed as in the manufacturing process of a semiconductor device. In the photolithography employed for the manufacture of an LCD device, a resist coating film is formed on a glass substrate, followed by exposing the coating film to light in a predetermined pattern and subsequently developing the patterned coating film. Further, a semiconductor layer, an insulating layer and an electrode layer formed on the substrate are selectively etched to form a thin film of ITO (indium tin oxide), an electrode pattern, etc.
A so-called spin coating method is employed for coating an LCD substrate with a resist solution. A spin coater disclosed in, for example, U.S. Pat. No. 5,688,322 is employed for performing the spin coating treatment. In the spin coater disclosed in this prior art, an LCD substrate is held by vacuum suction by a spin chuck. Also, a solvent and a resist are supplied to the substrate, and an upper opening of a rotary is closed by a lid. Under this condition, the spin chuck and the rotary cup are rotated in synchronism. In this case, the coating amount of the resist, which is attached to the substrate, is only 10 to 20% of the supplied amount, with the remaining 80 to 90% of the supplied resist being discharged into a drain cup. The discharged resist solution is partly recycled for reuse. However, most of the discharged resolution is discarded.
In recent years, the LCD substrate is enlarged from 650.times.550 mm to 830.times.650 mm. If the LCD substrate is further enlarged in future, the consumption of the resist solution is further increased. Since the resist solution is wasted in a large amount in the conventional spin coating method as pointed out above, it is of high importance to decrease the waste of the resist solution.